[OpenTRV-interest] OpenTRV crystal frequency?

[Derek Jennings]

I was actually intending to use a clone with the 328
http://hobbycomponents.com/index.php/dvbd/dvbd-ardu/ardu-dvbd/arduino-compatible-3-3v-pro-mini.htmlso
code space will not be a problem.

What is the rationale for the 32kHz crystal? Is it being used to provide
timing for the radio transceiver?

Thanks Derek


On 11 February 2014 20:54, Damon Hart-Davis <EMAIL ADDRESS HIDDEN> wrote:

> Actually, the Pro Mini uses the 168:
>
> http://arduino.cc/en/Main/ArduinoBoardProMini
>
> which means not enough code space for the OpenTRV code as it stands, but
> it could probably be squeezed back in to 16kB with a little effort.
>
> Rgds
>
> Damon
>
>
> On 11 Feb 2014, at 20:52, Damon Hart-Davis <EMAIL ADDRESS HIDDEN> wrote:
>
> > Hi,
> >
> > The crystal requency on the REV1 AVR board is 32768Hz, ie about 32kHz
> rather than 32MHz.
> >
> > Internally the RC oscillator runs at 8MHz and is prescaled to 1MHz (or
> lower) for the CPU clock.
> >
> > Your board might do fine.  Check that there are no clashes of our pin
> uses on REV1 with other things going on on the Pro Mini.  You would need to
> fit 32768Hz crystal.
> >
> > Rgds
> >
> > Damon
> >
> > On 10 Feb 2014, at 16:02, Derek Jennings <EMAIL ADDRESS HIDDEN> wrote:
> >
> >> Hi New subscriber to the OpenTRV list here.
> >> Maybe this question has already been answered. but I have not yet found
> the list archive.
> >>
> >> I notice from the OpenTRV schematic that you are using a 32MHz crystal
> for the ATMega328.  What are the implications of using a different
> frequency?
> >>
> >> I discovered OpenTRV after building an Arduino based Opentherm gateway
> between my spanking new Intergas boiler, and its (not so) intelligent
> Opentherm controller from Remaha.  You can see my project details at
> https://github.com/delboy711/ArduinoOpenTherm.
> >>
> >> One of the reasons I built it was because when my living room is up to
> temperature I wanted to tell the boiler to keep supplying heat for the
> radiators in other rooms. This naturally requires me to control the rads
> with motorised valves and to communicate with the valves which led to
> discovering OpenTRV.  (That's what I love about OpenSource. No matter what
> you want to do, someone, somewhere is already working on it!).
> >>
> >>
> >> I have a motorised valve on order from Conrad (the 561800-89 ), and had
> planned to use a 3.3V Arduino Pro Mini and an RFM22B radio unit to listen
> in on the protocol.  But the Pro Mini has an 8MHz resonator hence my
> question why OpenTRV uses 32MHz.
> >>
> >> Thanks
> >>
> >> Derek Jennings
> >> _______________________________________________
> >> OpenTRV-interest mailing list
> >> EMAIL ADDRESS HIDDEN
> >> http://lists.opentrv.org.uk/listinfo/opentrv-interest
> >
>
> _______________________________________________
> OpenTRV-interest mailing list
> EMAIL ADDRESS HIDDEN
> http://lists.opentrv.org.uk/listinfo/opentrv-interest
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.opentrv.org.uk/pipermail/opentrv-interest/attachments/20140211/4ba24143/attachment.html>